DEVELOPING OF A NEW COMPREHENSIVE SPARK IGNITION ENGINES CODE FOR HEAT LOSS ANALYSIS WITHIN COMBUSTION CHAMBER WALLS

The objective of this work is to develop the existing a zero-dimensional model named ODES to provide detailed insights into the internal process of the modern high speed spark ignition engines. Therefore, it has been concentrated on the development of new sub models for incorporation in an extended form of ODES, as follows: - the existing semi-empirical combustion model has been replaced by a new comprehensive model, which is based on the turbulent flame speed in the combustion chamber. - the existing three wall heat transfer model has been replaced by a new one in which, the combustion chamber is divided in to three zones including cylinder head, cylinder wall, and piston head. The steady-state heat transfer equation is solved through finite difference method with replaced boundary and initial conditions. The results gave the temperature distribution of combustion chamber walls. The rate of heat losses from combustion chamber to the coolant is calculated by using the mean temperature of each part. The code has been extensively validated with respect to performance and heat transfer against experimental results obtained on XU7JP spark ignition engine with two kinds of fuel, gasoline and compresed natural gas and gave good agreement with available experimental

Extended semi-analytical model for the prediction of flow and concentration fields in a tangentially-fired furnace

Tangentially-fired furnaces (TFF) are one of the modified types of furnaces which have become more attractive in the field of industrial firing systems in recent years. Multi-zone thermodynamic models can be used to study the effect of different parameters on the operation of TFF readily and economically. Flow and mixing sub-model is a necessity in multi-zone models. In the present work, the semi-analytical model previously established by the authors for the prediction of the behavior of coaxial turbulent gaseous jets is extended to be used in a single-chamber TFF with square horizontal cross-sections and to form the flow and mixing sub-model of the future multi-zone model for the simulation of this TFF. A computer program is developed to implement the new extended model. Computational fluid dynamics (CFD) simulations are carried out to validate the results of the new model. In order to verify the CFD solution procedure, a turbulent round jet injected into cross flow is simulated. The calculated jet trajectory and velocity profile are compared with other experimental and numerical data and good agreement is observed. Results show that the present model can provide very fast and reasonable predictions of the flow and concentration fields in the TFF of interest

Computational fluid dynamics simulation of the combustion process, emission formation and the flow field in an in-direct injection diesel engine

In the present paper, the combustion process and emission formation in the Lister 8.1 I.D.I Diesel engine have been investigated using a Computational Fluid Dynamics (CFD) code. The utilized model includes detailed spray atomization, mixture formation and distribution model which enable modeling the combustion process in spray/wall and spray/swirl interactions along with flow configurations. The analysis considers both part load and full load states. The global properties are presented separately resolved for the swirl chamber (pre-chamber) and the main chamber. The results of model verify the fact that the equal amount of the fuel is burned in the main and pre-chamber at full load state while at part load the majority of the fuel is burned in the main chamber. Also, it is shown that the adherence of fuel spray on the pre-chamber walls is due to formation of a stagnation zone which prevents quick spray evaporation and plays an important role in the increase of soot mass fractions at this zone at full load conditions. The simulation results, such as the mean in-cylinder pressure, heat release rate and exhaust emissions are compared with the experimental data and show good agreement. This work also demonstrates the usefulness of multidimensional modeling for complex chamber geometries, such as in I.D.I Diesel engines, to gain more insight into the flow field, combustion process and emission formation

A semi-analytical model for the prediction of the behavior of turbulent coaxial gaseous jets

In diffusion combustion systems, fuel and oxidizer (usually air) are admitted into the combustion chamber separately in the form of turbulent jets. Most often, fuel enters the furnace from a round nozzle and air is admitted through an annulus surrounding the central fuel nozzle. Momentum of the fuel and air jets is utilized for directing the flame and controlling the mixture formation which is typically the rate-limiting step of the combustion process. Hence the behavior of turbulent coaxial jets must be well understood prior to any detailed analysis of these systems. In this study, a set of relations is proposed to predict the behavior of turbulent coaxial gaseous jets using curve-fits to the computational fluid dynamics (CFD) solutions and the fluid flow governing equations as well as the ideal gas equation of state. A computer program is developed to implement the presented model. Results are compared with existing data and reasonable agreement is observed. According to the results, the presented model makes sufficiently accurate estimates of the flow and concentration fields in a very short time

Three-dimensional energetic and exergetic analysis of the injection orientation of DI diesel engine under different engine speeds

Three-dimensional (3-D) computational code was implemented to solve conservation equations based on finite volume method as to simulate 1.8 L Ford diesel engine. Velocity and pressure of each computational cell is achieved by SIMPLE (semi-implicit method for pressure-linked equations) algorithm. For the exergetic aspect, the initial condition is set at 0.1 MPa and 300 K. The engine modeling is performed with 130 °, 140 °, and 150 ° with respect to x-axis under 1500 and 2500 rpm engine speeds. The results, however, indicate better air/fuel mixture (near stoichiometric equivalence ratio) for 130 ° of injection angle, albeit smaller spray droplets (lower sauter mean diameter) were introduced with 140 °. It is seen that higher soot and NOx mass fraction is attributed to 1500 rpm engine speed. The highest NOx and soot are exhausted at 130 ° and 150 ° of injection, respectively. Second law efficiency was calculated for different spray angle and engine speed schemes such that 36.62%, 30.2%, and 32.07% are associated with 130 °, 140 °, and 150 ° of injection angle under 1500 rpm, respectively. In terms of engine performance, that is, indicated mean effective pressure, indicated specific fuel consumption, and temperature, the best performance metrics are of 130 ° equal to 15.4 bar, 0.3856 kg/kW-h, and 2074.97 K under 1500 rpm, respectively. Instant irreversibility rate is the highest amount with peak value of 17.48 J/deg for 130 deg-1500 rpm, while 140 ° shows higher mean irreversibility rate over crank angle (CA) period

Energy and exergoeconomic analysis of the gas compression station: A case study

The aim of this study is to improve the gas turbine operating conditions, used in the gas compression station of Marand, from the energy, exergy and economic points. The most important problems of these turbines are the low thermal efficiency due to the high heat losses, consuming large amounts of natural gas at the gas turbine start-up time in the starter system, turbine dependence on external electrical energy sources, as well as the high costs of fuel supply for the turbine and power consumption in auxiliary equipments. In this study the application of heat recovery steam generator to reduce the heat losses and increase the efficiency of combined cycle besides the replacement of the inefficient existing starting system are suggested. Furthermore, the effects of inlet air temperature, load, pinch point and steam injection to the turbine combustor are investigated in the energy and exergy balance equations and the unit exergy cost rates. Moreover, the costs related to the start up of a gas turbine, the fuel consumption and electrical energy are estimated. Results reveal that suggestive system not only can make the gas compression station independent from the external energy sources, but it also can reinforce the efficiency of the system and reduce the carrying costs. As with the 0.5 kg.s-1 steam injection to the combustion chamber of the gas turbine, at the inlet air temperature of 288 K and the pinch point of 10 K, the efficiency of the combined cycle increases 5 percent. Also the economic saving of this suggested system is about 79.68 dollars per each functional hour of the gas turbine and for the station running in its full load and design condition the amount of economic savings will exceed to 247 000 dollars in month

Thermodynamic evaluation of gas compression station from the point of energy and exergy view with an approach to reduce energy consumptions and emissions: A case study

The objective of the present study is to evaluate the gas compression station installed in Marand city from the point of energy and exergy view with an approach to reduce energy consumptions and emissions. The use of exhaust gases thermal energy is investigated to produce steam and electrical power. This free extra electrical power can be used in electrical facilities of the gas turbine unit and the gas compression station can be independent from foreign electrical energy sources. Meanwhile replacement of existing gas turbine starting system and the effects of inlet air temperature, steam injection to the combustion chamber and the steam generator pinch point are studied on fuel consumption, net power production, nitrogen oxides emissions and irreversibilities in various loads. The results revealed that in the proposed gas compression station the produced electrical power from the generated steam in the minimum load and inlet air temperature of 288 K is more than the overall electrical energy consumptions. Steam injection with amount of 0.5 kg.s-1 to the combustion chamber increased the cycle efficiency from 34% to 37.5% and decreased the emission from 3.1 ppm to 0.45 ppm in full load condition