Effect of Hybrid Fuels of Aqueous Ammonia, Dimethyl Ether, Biodiesel and Diesel Fuel on Thermal Performance of Diesel Engine

Different fuel mixtures have been investigated by many researchers in a way to achieve high thermal efficiency and reducing the emissions [6-9]. Blending DME with diesel and bio-diesel was conducted to investigate their influence on the combustion process and emission production using single and pilot injection techniques [10].

Blends of diesel, biodiesel-diesel (B₈₀/D₂₀) and DME-biodiesel (DME₈₀/B₂₀) were tested on diesel engine equipped to a passenger car. The characteristics of combustion showed that a high pressure in the mixture (DME₈₀B₂₀) in comparison to pure diesel and the mixture (B₈₀D₂₀). However, mixture of DME and biodiesel revealed a minor peak when the pilot injection strategy is used. In terms of the emissions, the DME₈₀B₂₀ produced NO_x emissions higher than B₂₀D₈₀ and diesel. Whereas zero soot emissions were noticed in the single injection and pilot injection strategies. Mixing diesel, algal biodiesel, and diethyl-ether to examine the emissions production and performance of a small CI engine was studied [11]. The obtained results revealed that adding diethyl-ether enhance heat release rate, ultimate pressure within cylinder and the brake thermal efficiency. It can be attributed to the following parameters of the additive: high oxygen value, volatility, and great cetane-number. The accuracy of the variables (brake-thermal-efficiency, NO_x, brake-specific-fuel-consumption, CO, and HC) was examined by using correlation coefficient (0.9746 - 0.9999), mean absolute error of low range from (0.001 to 2.591), and low mean squared error (11.023).

A work was conducted to analyze the oil extracted from lemon peel to produce biodiesel fuel [12]. Various blends (diesel and lemon peel oil) of fuels based on volume were used of 10%, 20% and 30% at normal conditions of CI engine. The results revealed that 20% blend showed good performance and lowering the exhaust emissions. Furthermore, diethyl-ether of 5% and 10% with 20% blend of lemon peel oil were added. The brake-thermal-efficiency for (20% blend of lemon peel oil and 10% diethyl-ether) was increased by 3.7% at ultimate load compared to the 20% lemon peel oil. Correspondingly, the harmful emissions (HC, NO_x, CO) and soot at full load were significantly reduced by 24.4%, 16.9%, 11.8% and 12.5% compared to 20% lemon peel oil. Diesel fuel, 20% lemon peel oil and (10% diethyl-ether / 20% lemon peel oil) were tested at similar conditions using DIESEL-RK software. Both the experimental and the theoretical data showed that (10% diethyl-ether/20% lemon peel oil) improves the performance of the engine and condense the toxic emissions. Further study was conducted on a single cylinder CI engine to evaluate combustion, performance, and characteristics of emissions [13]. The fuel used were blends of diesel, diethyl-ether and WCSO biodiesel. Findings of blending (diesel/WCSO biodiesel) showed that B₂₀ achieved close engine characteristics to pure diesel. Next, B₂₀ was mixed with diethyl-ether at volume ratios of (5%, 10%, and 15%). An enhancement of (2.8%) in the cetane-index when an addition of 10% diethyl-ether with B20, as well as a noticeable reduction of (29%) in the viscosity.

Improving the properties of the fuel by adding 10 % DEE led to reduction in ignition delay and duration of combustion, while produced high value of peak in cylinder pressure. At full load, Noticeable decrease of BSFC by 3.2% and increase of BTE by 1.3% were found when adding 10% DEE compared to B₂₀. Therefore, the observations of diesel/biodiesel and DEE blends largely reduced the smoke by (3.6%) and CO by (49.9%) emissions compared to diesel, while the emissions of (HC) were enlarged.  The stability of combustion in CI engines is essential. Thus, a study was conducted to analyze quantitatively the combustion-characteristics that affect the stability of the combustion for engines powered with biodiesel-methanol blends [14]. The obtained results, at (2400) r/min and full load, revealed that a 10% volume basis of methanol boosts the ultimate pressure. In addition, the increase of methanol ratio was observed to increase the characteristics of combustion (distribution range of low Ea, the number of PIP) and the difference of pressure.  Mixing dimethyl-ether, methyl-deaconate and biodiesel using (air-side) and (fuel-side) techniques was studied using counter flow flame-modeling [15]. Flame temperature profiles and heat release rate were analyzed when DME and MD mixed together in order to show the kinetic variances in combustion modes between pre- and post-mixing of biodiesel and dimethyl-ether. The findings showed that both additions of dimethyl-ether (air and fuel sides) can slightly increase the ultimate temperature and expand the reactions areas of flames. In the flame zone, DME and MD represent mainly oxidized and two different oxidation regions respectively. Premixing DME with fuel dehydrogenate MD by improving OH and H formation. The physicochemical properties of blending DME and biodiesel were observed to be better than using each fuel separately. A study was carried out to investigate in-depth the characteristics of combustion when Biodiesel and DME were blended using skeletal mechanism [16]. The approach involves four sub mechanisms related to ester sets, fuels, emissions, and small molecules. Methyl group (palmitate, stearate, linoleate, n-decane and 5-decenoate) were employed to reflect the behavior of combustion of various forms of biodiesel. The results showed that the characteristics of emissions and combustion of mixing DME with biodiesel fuel can be achieved by the mechanism. In addition, the increase of DME ratio led to an increase in the ignition delay and peak pressure within the cylinder, however, soot production was decreased.  To improve the usage of methanol in the compression engines, an experimental study was conducted using three ratios of (diethyl-ether and n-octanol) to enhance the ignition and co-solvents in diesel engines [17]. The first part of the work was conducted under various temperature range (10℃, 20℃, and 30℃) of and involved blends of methanol (pure and hydrous) with biodiesel extracted out of waste cooking oil. The findings of mixing biodiesel with pure methanol observed to be stable at all sets of temperatures. As a co-solvent, n-octanol was added to the mixture of biodiesel and hydrous-methanol to enhance the solubility. The ratios of blends were as follow: (15%- 25%- and 35%) of methanol, n-octanol and diethyl ether rate of (10%) and (2.5%) respectively. The results showed that the lowest value of the ultimate in cylinder pressure, pressure rise-rate and heat release-rate were observed in the blends of (biodiesel/ methanol/ diethyl ether and n-octanol) compared with biodiesel only. Moreover, an increase in the brake-specific-fuel consumption, smoke and CO levels were observed, whereas the thermal efficiency and NO_x levels and exhaust emissions were reduced. A study was conducted used a hybrid fuel prepared by mixing (Pongamia oil/ hydrated-ethanol 95% purity and butanol) on CI engine [18]. The findings showed that (Pongamia oil) properties such as viscosity and density were decreased significantly when blended with ethanol. The magnitude of brake-thermal efficiency showed to be similarly for hybrid fuel and pure diesel. Decrease in the NO_x, CO₂ and SO₂ emissions produced by hybrid fuels were observed. A numerical investigation was applied on homogeneous compression ignition engine using various ratios of mixtures of DME, methanol and pure diesel [19]. The investigation comprised two stages: the first, performance and combustion characteristics were discussed when two or three fuel blended, secondly, comparison and examination of engine speed and EGR effect of (20%) mass ratio were carried out for two blends of minimum and maximum ratio of diesel fuel. The indications of the results showed that mixing 50% diesel, 20% DME and 30% methanol at rpm of 1400 produces high pressure, the best mechanical efficiency of 35% and the heat accumulated of 330.569 J. However, 80% diesel and 20% methanol at rpm of 2000 the EGR 20 low combustive performance and efficiency. the blend of 60% diesel, 30% DME and 10% methanol produced the ultimate exergy performance-coefficient of 2.063 owing to the lowest irreversibility and high work. A further study examined the influence of various ratios of diethyl-ether, biodiesel, and diesel fuel on the characteristics of a diesel engine [20]. The mixtures of (diesel 80% /biodiesel 20%) and (2.5%-5% -7.5%-and 10%) of diethyl-ether with (biodiesel-diesel) were prepared and examined on a single-cylinder/diesel, 4 stroke, direct-injection GDI engine. In addition, the GDI-engine was running at five various loads and constant speed. The results of adding 10% diethyl ether showed an apparent decrease in the BTE 17.39% compared to diesel fuel, however, an increase in the BSFC of 29.15% was observed. Moreover, the mixtures of diethyl/ether, biodiesel and pure-diesel showed mitigation in the smoke, HC, and NO_x emissions of 4.12%, 12.89% and 8.84% respectively compared to pure diesel. High ratios of diethyl-ether with diesel increased the CO emissions. However, CO and CO₂ dropped down at high loads of the engine. Consequently, diethyl-ether can be employed as a favorable addition of 10% to the biodiesel/ diesel with no modifications to the engine.  An experimental comparison was conducted to show the influence of the addition of diethyl-ether and methyl-tertiary-butyl-ether to diesel and biodiesel mixtures on CI engines [21]. Fractions based volume of ethers of (5% and 10%) mixed with 50% diesel and the rest is biodiesel. The findings of (50% diesel/45% biodiesel / 5% diethyl-ether) mixture revealed an increase of (5.3%) in the thermal-efficiency compared to other mixtures. In contrast, mixtures of (50% diesel/45% biodiesel / 5% diethyl-ether) and (50% diesel/45% biodiesel / 5% methyl-tertiary-butyl-ether) showed a good reduction in the emission of CO of 14.8% and 8.1% respectively compared to pure diesel. Furthermore, NO_x emission of the blends (50% diesel/40% biodiesel / 10% diethyl-ether) and (50% diesel/40% biodiesel / 10% methyl-tertiary-butyl-ether) was reduced by (32%) and (8.8%) respectively at full load. In terms of HC emission, all ether group showed significant decrease compared to diesel and biodiesel, whereas blend of (50% diesel/45% biodiesel / 5% diethyl-ether) produced lower smoke than pure diesel.

A new technique that added nano-particles, the titanium oxide (TiO₂), to blend of (diesel- biodiesel (Jojoba) - alcohol) in order to enhance the combustion and performance of the CI engines [22]. The fractions used in the study were as follow: TiO₂ of 25 and 50 mg/L, 40% diesel, 50% biodiesel, and 10% n-butanol. The results showed that heat release-rate and ultimate pressure are grown by (1.5%) and (2%) respectively when the nanoparticles of TiO₂ was added to blend of fuel. Exhaust emissions CO and HC showed an apparent reduction of (30%) and (50%) respectively. On the other hand, emissions of NO_x showed an increase of 30%. In conclusion, to obtain high thermal-efficiency and ultra-reduction of HC and CO emissions the following blends fuel (TiO₂, 50% jatropha biodiesel, 40 5 diesel and 10% n-butanol) is recommended. A study used a hybrid multi-criteria decision making (MCDM) approaches to overcome the difficulties of obtaining the optimum parameters of good performance and characteristics combustion of CI engines [23]. Test conditions were a 10.8 kW resistive load and constant-speed. The obtained outcomes showed that the best hybrid models are ANP-MOORA and SWARA-MOORA, as well as the optimal fuels were biodiesel extracted from animal fat and vegetable, diesel, and the blend fuels. Base on the results, both hybrid models showed that biodiesel of 20% is the best fuel.  A numerical model was developed using artificial-neural-network to investigate the predicted outcomes of exhaust emissions and brake specific-energy consumption. The study proposed to work on a CI (single cylinder) compression engine fueled with (diesel- biodiesel (palm) - ethanol) mixtures [24]. The results were obtained at conditions of load range from (20-100%) and constant speed of 1500 rpm. The obtained results showed that the predicted performance and emissions had a range of correlation coefficient between (0.99329 and 0.99875) and the magnitude of the mean square error of (0.000179082 to 0.000465809). A comparison was made between the predicted data and the experimental work to find the best operating conditions for the CI engine. For instance, multi-performance-characteristics index values were found to be the highest (0.705/ numerical model) and (0.718 /experimental) for the blend (85% diesel/ 10% biodiesel /5% ethanol) at 20% engine load. An experimental work conducted to evaluate the combustion of the blends (biodiesel/bioethanol/diesel) on single-cylinder CI engine [25]. The brake thermal-efficiency and brake specific-fuel-consumption, CO, NO_x, and smoke emissions were evaluated. An approach of kernel based-extreme-learning machine is proposed to collect the theoretical data of engine performance and emissions. The experimental results of the blend (biodiesel/bioethanol/diesel) showed a reduction in the brake-specific fuel-consumption, CO, and smoke, however, an increase in the brake-thermal-efficiency was noticed. The mean absolute-percentage errors are brake-thermal-efficiency (1.482%), the brake-specific fuel-consumption (1.363%), CO (4.597%), NO_x (2.224%) and smoke (2.090%). Finally, the findings of K-ELM technique are in good agreement with experimental data. Thus, its reliable to evaluate the performance and the emissions of the exhaust for a single-diesel engine fueled with (biodiesel/bioethanol/diesel) blends.  Fractions of biogas with diesel and waste plastic oil were studied on diesel engine to examine the improvement in the performance and emissions [26]. The studied fractions of biogas based on the volume were (10%, 20%, 30%, and 40%), and these fractions were added to (20%) waste plastic oil and diesel blends. The response-surface method was proposed and employed to evaluate the desirable engine performance such as high exergy efficiency, HC emissions. The values of the engine parameters were: energy efficiency (18.6%), exergy efficiency (50.05%), BSFC (0.46 kg/kWh), and CO (0.16 ppm), HC (41.28 ppm), and NO_x (107.81 ppm) emissions. The results found at engine load of (57.12%), compression ratios of 18, and (20% biogas / 20% WPO- 60% diesel) blend. Optimization of engine behavior was studied using algorithms of meta-heuristic-optimization method combined with experimental data [27]. In addition, the artificial neural networks were hired to estimate the emissions and performance of diesel engine fueled with hybrid blends of biodiesel. In order to examine the validity of the ANN method, 4 statistical benchmarks R2 and MSE were employed.  The obtained results showed that ANN and RSM were outstanding modeling approaches with decent accuracy. ANN technique predicted performance better than RSM of [R2=0.978 for BTE] and [R₂=0.960 for BTE], respectively. However, the 5ml additive of (PJB₂₀) biodiesel blend improved the BTE by (52.8%) and decreased BSFC (34.9%) at full load. The smoke and CO₂ emissions were reduced by 7.1% and 19.14% respectively compared to pure diesel. The focus on obtaining hybrid blends fuel out of oil generated -(karanja) biodiesel-diesel is currently the aim of any researchers [28]. The (karanja) biodiesel and (pyrolysis) oil were blended to boost the low value of calorific in the biodiesel. On a single-cylinder CI engine, the examined blends are [10% of tire/pyrolysis (TP), 20% karanja/biodiesel (KB) and 70% of diesel], in addition [20% of tire/pyrolysis (TP), 10% karanja/biodiesel (KB) and 70% diesel]. The results of the two blends showed high combustion characteristics and performance compared to pure diesel.   An experimental investigation was implemented to highlights the advantage of using hydrogen on CI engines fueled with [ethanol-jatropha biodiesel] blend [29]. Various engine loads of (25%, 50%, 75% and 100%), five durations of hydrogen injection of (1200/ 2500/ 3700/ 4500 and 6000 μs) and 1500 r.p.m speed were used. The observations showed that the blend [10% ethanol- 90% (jatropha) biodiesel] enhance slightly the parameters of performance, exergy, and combustion. Improvements were seen in brake-thermal efficiency, exergetic efficiency, exergy destruction-rate and entropy generation of (2.09-2.92%), (1.85-2.67%), (1.72-7.05%) and (4.26-9.47%) respectively when a slight amount of hydrogen injected at 2500 μs. Thus, injecting large amount of hydrogen into the hybrid mixture remarkably decreases the UHC and CO emissions, however, slightly increases the NO_x emissions.

The scope of previous studies indicated several points like; numerical investigation in most of studies are absent. Furthermore, no hybrid fuel consists of different blends used in diesel engine is seen as the literature articles showed the single use of (biodiesel, water ammonia solution and DME) along with diesel engine rather that combined form of hybrid fuel with different blends. These gaps can be bridged in the present work that aims to investigate numerically using Diesel-RK code the impact of using two different hybrid fuels content different blends of algae biodiesel, water ammonia solution and DME on the thermal parameters of constant speed dual fuel diesel engine.

The current wok involves the use of the DIESEL-RK program version (4.3.0.189) is intended for the calculation and optimization of two-stroke and four-stroke internal combustion engines. The program allows you to carry out thermal calculations, analysis, and research of the following types of internal combustion engines: diesel, gasoline spark both (carburetor and gasoline injection) and gas spark (conventional as well as pre chamber). DIESEL-RK belongs to the class of thermodynamic programs, where engine cylinders are considered in it as open thermodynamic systems. The diesel combustion model allows us to study a multi-fuel engine operating as a diesel engine. fuel and biofuels, including their mixtures with (diesel fuel) in different proportions. The chemical and physical behaviors of fuels can be specified by the user and saved in the program database. For each engine operating mode, you can set your own fuel [38].

In this study the combustion model of multizone was employed, and Diesel-RK software was used to solve the governing equations. Additional details about the formulation of the model used in this work were adopted from Al-Dawody and Bhatti [39], Al-Dawody and Edam [40].

4.1 Spray assessment model

An elemenatry-fuel-mass (EFM) has a speed, transfers between the injector towards the spary-tip at a short time step illustrated in Figure 1, which can be found from Eq. (1).

${{\left[ \frac{\text{U}}{\text{ }\!\!~\!\!\text{ }{{\text{U}}_{0}}} \right]}^{\frac{3}{2}}}=1-\frac{\text{l}}{{{\text{l}}_{\text{m}}}}$                         (1)

where: $\text{U}$: (EFM) current-speed, ${{\text{U}}_{{}^\circ }}$: (EFM) initial-speed at the nozzle-injector, $\text{l}$: the current distance between the (EFM) and the nozzle-injector ${{\text{l}}_{\text{m}}}$: the penetration length of EFM till the end in front of a spray. The differential Eq. (1) is solved partially as:

$3{{l}_{m~}}\left[ 1-{{\left[ 1-\frac{l}{{{l}_{m}}} \right]}^{0.333}} \right]-{{V}_{o}}{{\tau }_{k}}=0$                                     (2)

where: ${{\tau }_{k}}$ - travel period for the EFM to amount to the length $l~$from the nozzle injector.

image006.png

Figure 1. Illustration of the fuel-spray [41]

When (EFM) is stopped in a spray-tip $\left( l={{l}_{m}} \right)$ and ${{\tau }_{k}}={{\tau }_{m}}$.

Where: ${{\tau }_{m}}$- represents period of traveling for the (EFM) to amount the (spray’s front) before stopping.

Eq. (2) then rewritten as:

${{\text{l}}_{\text{m}}}={{\text{V}}_{\text{o }\!\!~\!\!\text{ }}}\frac{{{\text{ }\!\!\tau\!\!\text{ }}_{\text{m}}}}{3}\left( 3 \right)$                          (3)

From Eqs. (1) to (3) the (EFM) current-speed and length were obtained as follow:

$V={{V}_{o}}{{\left[ 1-\frac{{{\tau }_{k}}}{{{\tau }_{m}}} \right]}^{2}}$                             (4)

$l={{l}_{m}}\left[ 1-{{\left[ 1-\frac{{{\tau }_{k}}}{{{\tau }_{m}}} \right]}^{3}} \right]$                                    (5)

4.2 Heat release model

Four phases during the combustion process are observed, each phase has specific physical and chemical characteristics restricting the burning rate-speed. Those phases are described below [42]:

1. Ignition delay period phase can be obtained from:

 $\tau =\sqrt{\frac{T}{P}}~*{{e}^{\left( \frac{{{E}_{a}}}{8,312T}-\frac{70}{CN+25} \right)}}*~3.8*{{10}^{-6}}*\left( n*1-1.6*{{10}^{-4}} \right)$                      (6)

2. The process of combustion for the mixtures of (air/fuel vapor) is called premixed combustion-phase:

$\frac{dx}{dt}={{\varphi }_{1}}\left( \frac{d{{\sigma }_{u}}}{d\tau } \right)+~{{\varphi }_{o}}*\left[ \left( {{\sigma }_{ud}}-{{x}_{o}} \right)\left( 0.1{{\sigma }_{ud}}+{{x}_{o}} \right){{A}_{o}}\left( \frac{{{m}_{f}}}{{{V}_{i}}} \right) \right]$                                          (7)

3. The process when the fuel is directly injected and combusted is called diffusive combustion-phase.

$\frac{dx}{d\tau }={{\varphi }_{2}}\left( \left( {{\sigma }_{u}}-x \right)\left( \varnothing -x \right)*{{A}_{2}}\left( \frac{{{m}_{f}}}{{{V}_{c}}} \right) \right)+~{{\varphi }_{1}}\left( \frac{d{{\sigma }_{u}}}{d\tau } \right)$                                          (8)

4. The process of burning fuel when the injection is completed is called late burning-phase:

$\frac{dx}{d\tau }=\left( 1-x \right)\left( {{\varepsilon }_{b}}\varnothing -x \right)*~{{\varphi }_{3}}{{K}_{T}}~{{A}_{3}}$                               (9)

${{\varphi }_{3}}={{\varphi }_{2}}={{\varphi }_{1}}={{\varphi }_{o}}~$represents a function that describes the combustion is completed in the zones of fuel-vapor:

$\phi =1-({{A}_{1}}/{{\varepsilon }_{b}}\varnothing -x)\frac{dx}{dt}~\left\{ {{r}_{v}}+\underset{i=1}{\overset{{{m}_{w}}}{\mathop \sum }}\,\left[ {{r}_{wi}}\text{*}300\text{*}{{e}^{\left( \frac{-16000}{2500+{{r}_{wi}}} \right)}} \right] \right\}$                                   (10)

where: ε_b represents the efficiency of air-use, r_v relative-evaporation rate in the front and zones of the environment, ϕ the equivalence-ratio, r_wi the relative-evaporation-rate through different zones inside wall surface-flow.

4.3 NO_x formation modeling

The ordinary mixing of (NO₂/ NO) lead to produce of (NO_x emissions). In the current study, employing the software of (Diesel-RK), the method of Zel'Dovich is utilized [43]:

${{O}_{2}}\leftrightarrow 2O$                               (11)

$O+{{N}_{2}}\leftrightarrow NO+N$                              (12)

${{O}_{2}}+N\leftrightarrow NO~+O$                                 (13)

The concentration of atomic-oxygen influences the reaction-rate as shown in Eq. (13). The volume-concentration of (NO) is calculated using the equation below:

$\frac{d\left[ NO \right]}{d\theta }=\frac{{{e}^{-{}^{38020}/{}_{{{T}_{z}}}}}{{\left[ {{N}_{2}} \right]}_{e}}{{\left[ O \right]}_{e}}\left( 1-{{\left( \frac{\left[ NO \right]}{{{\left[ NO \right]}_{e}}} \right)}^{2}} \right)*2.33*{{10}^{7}}P}{R{{T}_{z}}\left[ 1+\left( {}^{2365}/{}_{{{T}_{z}}} \right){{e}^{{}^{3365}/{}_{{{T}_{z}}}}}{}^{\left[ NO \right]}/{}_{{{\left[ {{O}_{2}} \right]}_{e}}} \right]}\left[ \frac{1}{rps} \right]$                                       (14)

4.4 Soot concentration modeling

The incomplete (HC) combustion will result tiny black carbon-particles called soot [44]. The concentration of soot in the engine’ exhaust at the standard conditions is found to be:

$\left[ C \right]=\underset{{{\theta }_{B}}}{\overset{480}{\mathop \int }}\,\frac{d\left[ C \right]}{d\tau }\frac{d\theta }{6n}{{\left[ \frac{0.1}{P} \right]}^{\gamma }}$                              (15)

The level of Hartidge smoke is calculated as follow:

$\text{Hartidge}=100*\left[ 1-{{e}^{\left( -24226\left[ C \right] \right)}}*0.9545 \right]$                             (16)

Eq. (17) is used to define the Particulate-Matter (PM) as a function of BSN:

$\left[ PM \right]=565*{{\left[ \ln \frac{10}{10-Bosch} \right]}^{1.206}}$                              (17)

The air pollutant emission equation (SE) is another important equation combines (PM) and (NOx) pollutants [45]:

$SE={{C}_{PM}}\left[ \frac{PM}{0.15} \right]+{{C}_{NO}}\left[ \frac{N{{O}_{x}}}{7} \right]$                                   (18)

4.5 Software validation

The reliability of the (Diesel-RK) solver is checked via the comparison with the results of study conducted by Reiter and Kong [46]. Similar engine details as well as operating conditions are used as shown in Table 4. The pressure development curve through per crank angle is shown in Figure 2. The turbocharged engine is turned to dual fuel mode working on 60% diesel and 40% ammonia) on energy basis. The present study shows same trend with slight deviation around 5% compared to the work of Reiter and Kong [46]. The peak pressure is 7.8393 Mpa occurs at 6 deg. ATDC while the present work reported pressure of 7.466 MPa at 5 deg. ATDC.

Figure 3 illustrates how the volumetric concentration of CO₂ impacted by NH3 replacement in diesel. Both curves have similar attitude with minor difference. For mono fuel diesel (100% operation). The CO₂ concentration is deviated by 2.083% from the results obtained by Reiter and Kong [46] while for (60% diesel+40% NH3) on dual fuel mode the obtained results is differed by 6%. Its worthy to say that the simulation software is trusted enough and can be considered an efficient tool to simulate the combustion process in diesel engine.

Table 4. Engine’s information used for validation [46]

image008.png

Figure 2. Validation of cylinder pressure profile

image010.png

Figure 3. Validation of CO₂ concentration per % diesel energy

The numerical software Diesel-RK is used to simulate diesel engine working on two modes, first one refers to the base line operation on plain diesel and the dual fuel mode with the use two hybrid fuels. The hybrid fuels involve different combination on energy basis of aqueous ammonia, DME, and biodiesel in addition to neat diesel. The overall conclusions are summarized as follows:

1. The Pressure, and heat release dropped when engine turned to dual fuel mode whether hybrid 1 or hybrid 2 is used.

2. The presence of NH₄OH in both hybrid fuels attends to prolong the delay-period because it has a lower cetane-number and a slower combustion-reaction.

3. Clear increase in the BSFC with use of hybrid 1 and hybrid 2 as well as slight decrease in BTE.

4. Incredible reductions in (NO_x) emissions observed as follows: 48.12% for hybrid 1 and 37% for hybrid 2.

5. The BSN is strikingly reduced by 51.2% and 53.2%, when hybrid1 and hybrid 2 is respectively.

6. The findings point out that using hybrid 2 (40% DF+40% NH₄OH+20% biodiesel) is preferable more than hybrid 1 (20% DF+50% NH₄OH+30% DME).

7. Further numerical simulation is suggested to indicate how these hybrid blends can response under variable engine speed, compression ratio and injection timing accordingly.

8. An experimental investigation is suggested to study the influence of utilizing such hybrid fuels on the performance, combustion, and emissions characteristics of the engine.

9. The economic, maintenance and cost analysis with the use of such fuels in dual fuel diesel engine is suggested.