Gas-Cylinder Motor Vehicle

a vehicle with an engine that runs on gaseous fuels stored in a compressed or liquefied state in cylinders mounted on the chassis.

Natural gases extracted from gas fields or obtained during petroleum production and refining are stored in a compressed state. Coke gas, a by-product of coal processing, is also stored in a compressed state. In order to assure an adequate running supply for the vehicle, compressed gases are delivered into the cylinders at a pressure of 20 meganewtons (MN) per m² (200 kilograms-force [kgf] per cm²).

Gases stored in a liquefied state may be subdivided into two groups. The first consists of butane-propane and butylene-propylene gases, which are converted to a liquid state at normal temperatures and under comparatively low pressure; they are kept in steel cylinders designed to withstand a pressure of 1.6 MN/m² (16 kgf/cm²). The second includes methane gas, which is converted to a liquid at atmospheric pressure and at a temperature of — 161.3° C; special isothermic cylinders made of cold-resistant material and designed to withstand a pressure of 1 MN/m² (10 kgf/cm²) are needed to store and transport it.

Among the basic advantages of gas-cylinder motor vehicles over vehicles running on liquid fuels are less wear on the engine parts, longer service life of the oil, the possibility of increasing engine power by raising engine compression, greater fuel economy, lower fuel cost, and low toxicity of exhaust gases. General use of gas-cylinder vehicles is dependent upon the creation of a network of tank-filling stations; the absence of such stations has delayed development of this mode of transport.

In the USSR the first models of gas-cylinder vehicles were made at the beginning of the 1930’s. Assembly-line production of gas-cylinder vehicles running on compressed gases was begun in 1939; production of vehicles running on liquefied gases began in 1953. Gas-cylinder motor vehicles are categorized as either universal (that is, running both on gas and on gasoline) or specialized (with engines adapted for gas only).

The gas-cylinder apparatus of a vehicle operating on compressed gas includes some five to eight cylinders, usually positioned below the cargo platform. Upon leaving the cylinder, the gas flows through a heater, a main valve, and a filter into a two-step reducer, where its pressure is lowered to approximately atmospheric pressure. The outlet of the reducer is equipped with a metering device that ensures that the necessary amount of gas is supplied to the carburetor-blender, in which the gas is mixed with air. The gas-air mixture then goes to the engine cylinders.

The gas-cylinder apparatus of a vehicle operating on liquefied gas includes one cylinder, filled with liquid to 90 percent of its capacity; the additional 10 percent volume at the top of the cylinder contains a vapor cushion, which allows for the heat expansion of the liquid. When the cold engine is started up, the fuel enters it in a gaseous state from the upper part of the cylinder. The warmed-up engine runs on fuel supplied from the lower part of the cylinder. This fuel flows through a main valve to an evaporator, where it is transformed from a liquid to a gaseous state by the heat of the hot water in the engine’s cooling system. The evaporated fuel passes through felt and gauze filters, through a two-step gas reducer, and into a two-chamber gas blender in which it is mixed with air in the proper proportion. The gas-air mixture is drawn into the engine cylinders and is burned as in a regular engine.

Liquefied methane is normally used for several purposes at the same time: as a cold source to keep the temperature in the cargo compartment low (for example, for the transport of perishables) and as a fuel for the engine. Upon leaving its isothermic cylinder, methane passes through a battery of heat-exchangers in which it evaporates, taking on heat from the surrounding air. It then enters an automatic switching device and a two-step reducer and passes on to the gas blender, from which it enters the engine cylinders.

The basic technical characteristics of modern gas-cylinder motor vehicles are given in Table 1.