Diesel-to-natural gas engine conversion is an important economic task. In this modification the gas engine has some fundamental differences from the diesel: forced ignition is replaced by Compression ignition; as a rule, external mixture formation instead internal mixture formation; the quantitative load control using throttle - instead quality load control. The latter is one of the main reasons for the deterioration of the fuel economy of the gas engine especially at low loads, because of the significant increase in pumping losses when reducing the load by throttling. The greatest value of such losses is on the idle speed. The authors considered the possibility of increasing the efficiency of the gas modification due to the implementation of the Miller cycle, where the load reduction is achieved by variable valve timing - mainly the valve Duration and intake valve closing angle. In this case, the load reduction is achieved without the use of throttling the fuel / air mixture. The analysis is performed using a calculation method, which was developed a special program takes into account the main physical processes of the gas engine at low operating conditions. The authors considered several options for improving fuel economy at engine low load operation for the engine KAMAZ-820.74-300, including the possibility of using lean air fuel mixture, increasing the compression ratio, load management using changing valve timing. The authors defined the values of temperature and pressure at characteristic points of the pressure volume diagram, and the values of indicated thermal efficiency of an engine, fuel consumption and other parameters for the five variants of idling. The authors presented the calculated pressure volume diagrams of a Miller cycle at idle. The authors have shown the best option, where possible fuel economy improvement at idle is 25 % compared to the base engine.
The improvement of the balance of reciprocating internal combustion engines is an important task of improving the design, the solution of which allows to improve the environmental properties of the automobile by reducing vibration and noise. Perturbations from the action of overturning (reactive) torque are substantially different from the action of inertial forces and moments. Its common quantitative evaluation in existing methods of analysis is missing, which complicates a general analysis of the balance. The authors proposed to use as the same for all sources of imbalance the measures of perturbation value the maximum for the period of the pulse value, developed a software system that allow to perform such an assessment of unbalance for three-cylinder reciprocating engine type L3 with the specified weight and size characteristics and modes of operation. The mechanism is proposed to partially balance the reactive torque of the engine, the optimal parameters for the field of specified modes of operation was found. Using the developed complex the analytical quantification of unbalance from the action of overturning moment of three-cylinder engine with typical mass-dimensional parameters as when balancing with proposed method and without it was made. For a typical scheme of moment partial balancing of forces of inertia of the first order in considered engine the assessments of disturbances were made and their effect on different modes was studied. It was found out that in the engine of L3 type unbalance from the action of reactive torque at low and medium frequencies of rotation makes a major contribution to vibroactivity of engine surpassing in values of the impulse contribution from the residual unbalance from the moment of inertia of the first order inherent to typical designs. The mechanism allows to decrease this imbalance several times.
Methane, as an alternative to traditional motor fuels, is the most perspective for the incoming decades of the current century. The most widely spread method of the modification of diesel engines for operating with methane is a conversion of a basic model by changing both the way of ignition - compulsory spark ignition instead of self-ignition by compression, and the method of power control - quantitative, with the help of a throttle in case of a gas version, instead of qualitative in a diesel version. The main task of such conversion is to achieve the best possible energy and economic performance of the engine. Moreover, the peculiarity of the operation procedure of the gas engine, the necessity to avoid detonation combustion, should be taken into account. Consequently, in the process of converting a diesel engine into a gas one manufacturers have to decrease both the compression ratio and boost pressure, which leads to decline in engine efficiency. The authors found out, that there is a potential possibility to achieve much better eco-nomic and power characteristics of gas engines by applying Miller cycle to the operation procedure. In this case it becomes possible having very high geometric compression ratio and corresponding high val-ues of gas expansion to obtain relatively low values of actual compression ratio. This is the value that can lead to detonation combustion. The program of calculating the characteristics of operation procedure of Miller-cycle gas engines was worked out. The authors suggested a system of calculation, according to which detonation behavior is estimated on the basis of actual data of a particular model of the engine. Due to such analyses of the particular model of the engine we found out actual maximum values of compression pressure and compression temperature, which do not lead to the onset of detonation. So it may be stated that the parameter value that significantly increases the overall efficiency of the Miller-cycle gas engine, created on the base of Kamaz engines, is found.
The analysis of the promising direction of development of energy installations of land transport is conducted. To date, in view of the emerging problems of depletion of oil resources and environmental safety in transport, in some popular science publications and in the media, the idea of the upcoming transition of motor vehicles to electric traction is actively awakening. However, in the opinion of the overwhelming majority of authoritative specialists in the automotive industry, this idea is premature and does not have a serious scientific substantiation. Currently, there is a large investigated potential of replacing oil with alternative energy products, the resource base of which, in some cases, significantly exceeds the traditional raw material base of oil fuels. Wide opportunities to solve the problem associated with the predicted depletion of oil resources are enclosed in the use of natural gases (primarily methane) and vegetable (biological) raw materials for the production of motor fuel. The development of alternative energy is universally considered one of the promising ways to solve the problems of energy supply, both in the field of constantly growing energy consumption in general, and in the direction of the future development of the energy balance of the transport complex. Thus, it is possible to assert with confidence that the domestic automobile transport is guaranteed to be provided with motor fuel for many decades. In addition, the current opinion about the high energy and environmental efficiency of electric motor transport is, in its essence, not unambiguous and for a number of indicators the electric vehicle is significantly inferior to a vehicle with a traditional internal combustion engine. In this article, on the basis of a reasoned analysis involving the opinions of a large number of authoritative specialists in the global automotive industry, this statement is proved.
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