The Humphrey Pump

Progress, Volume IX, Issue 10, 1 June 1914, Page 1123

The Humphrey Pump

By F. C. BUNYARD, Engineer to Cambridge Borough Council

A short Description of its Construction and Working

' The information presented in this paper and its accompanying drawings have been compiled chiefly from literature and drawings supplied by the Pump and Power Company, of London, of which company Mr. H. A. Humphrey, the inventor of the pump, is managing director. It has been amplified by reference to sundry engineering periodicals, and to the proceedings of various mechanical societies, principally to a paper read by Mr. 11. A. Humphrey before the Manchester Association of Engineers. Many parts of the various articles have been condensed, and many features of construction have been omitted, the mention of which was not vital to a clear description of the apparatus. The Humphrey Pump, being of a type peculiarly suitable for the needs of the civil engineer in raising water for irrigation and domestic supply, sewage raising, etc., 1 thought the subject would not be of too mechanical a nature to interest the members of this Institute. I hope that the information here presented will be of some little use to those members who, like myself, have to deal with the raising of water and other liquids by pumping. In the present paper it is only intended to deal with the subject from the broad point of view. The simplest type of pump and only one type of valve gear will be described, to illustrate the kind of device that has given satisfaction. As I have been instructed by the Cambridge Borough Council to report upon the augmentation of our water pumping and distributing system, and wishing to recommend the installing of the latest and most economical type of plant, I entered into correspondence with the Humphrey Pump people, having been impressed by the success of their large installation at Chingford, England, where a plant capable of lifting 180 million gallons of water per day to a height of from 25 to 30 feet is in successful operation. To the Pump and Power Company of London I am indebted for much valuable information. The simplicity, ingenuity, and high economy of the Humphrey Pump has excited the greatest interest amongst engineers. GENERAL DESCRIPTION OF A HUMPHREY PUMP The pump described is of the four cycle type, and was the one that was exhibited in operation at the Brussels Exhibition, where after trials it was awarded the Grand Prize as a gas engine, and the Grand Prize as a pump. The pump works upon the principle of internal combustion. “The energy of expansion of an ignited combustible mixture is applied to one end of a column of liquid so as to cause it to propel the column along the discharge pipe and cause it to oscillate in the pipe under such conditions of energy of the moving liquid that everything necessary for the next ignition is performed during one or more oscillations, and wholly or partly due to it or them.”

* A paper read at the annual meeting of the Institute of Local Government Engineers at Auckland in March last.

The pump may be worked by town gas, producer gas, suction gas, petrol, or kerosene. The pump itself, as a prime mover and machine, is simplicity itself, but the mathematical basis of its working is more complex. The construction of the pump will be readily seen on referring to drawing

The pumps work very quietly and smoothly owing to the valves being shut when explosion occurs', and the fact that the valves open and shut under very light pressure. The fuel consumption and first cost of these pumps for a given horse power in the water lifted, are less than any system, either

Diagram showing Working Cycle of Humphrey Pump Ato B —Explosive charge being compressed. BCharge ignited. Bto —Rise of pressure due to explosion Cto D—Gases expanding, doing work. DExhaust valve opens. Dto —Taking in water (and scavenging air) partly exhausting to E. Return stroke completing exhaust till valve closes at F. Exhaust valve closes. Fto —Compression of Cushion. Gto HCushion expanding. H—lnlet valve opens admitting fresh explosive charge. J—lnlet valve closes on return of water column. Jto K.—Compression of charge. KCharge ignited—commencing fresh cycle of operations. Compression pressure at ignition 56'5 lbs. sq. in. Explosion pressure 163 lbs. sq. in. Cushion pressure 185 lbs, sq. in. Pump delivery per working stroke 306 gallons. Head of water pumped against 39'4 feet. Horse power of pump 45 W.H.P.

A, and very little explanation is necessary except of the valve gear, which is also shown enlarged on drawing A. It will be noticed that there are no moving parts except the gas, exhaust and water valves, and their attendant locking gear. -There are no bearings, no flywheel, no crank shaft or connecting rods, no piston as generally used.

gas or steam. Under favourable conditions the Humphrey pump is the most economical method of pumping ever known. The pump will deal with the dirtiest of water. Experiments made at Chingford prove that there is no contamination of the water pumped by the exploding gases in the combustion chamber. The pump proper is built up of

three main castings the combustion chamber, the lower bend, and the water valve box. From the water valve box the discharge pipe leads to the elevated tank. The supply or suction tank embraces the water valve box, giving free access of water to the valves. These valves open inwardly, being held on their seats by light springs. At the head of the combustion chamber are fitted the inlet valve for gas and air admission, the exhaust valve, and the air scavenger valve. A simple system of locking bolts is arranged between these valves so that when the inlet valve opens and closes it locks itself shut, and with the same movement unlocks the exhaust and scavenger valves and vice versa. Therefore at each suction period in the combustion chamber these valves open in rotation. Normally the exhaust valve has a tendency to remain open and the inlet valve to remain shut through the action of light springs fitted to them. As the scavenger valve is not essential to the working of the smaller pumps it will for the present be left out of consideration. Should, however, any merriber desire an explanation of the use and action of this valve I will be pleased to give one. An indicator, fitted to a pump when working, and driven by clockwork at a uniform rate, would produce a diagram like that shown on Drawing B. For starting the pump one of two methods may be used: (1) By pumping an explosive mixture into the combustion chamber, and exploding same by hand operation of the ignition apparatus. (2) By pumping air only into the combustion chamber until the water column is forced well down to the lower end of same. The exhaust valve is then opened by means of the hand lever shown on Drawing A. Either of the above methods sets up a surging of the water column. At starting all valves are closed, the inlet valve being locked and the exhaust valve free. Combustion chamber, water valve box, and discharge pipe are full of water up to the level of the water in the supply tank. We will suppose that a charge of explosive mixture has been ignited by hand operation of the ignition apparatus. All valves being shut when the explosion takes place, the resultant increase in pressure acting upon the surface of the water forces it downwards in the pump and sets the whole water column in motion. The column of water attains kinetic energy, so that when these gases reach atmospheric pressure the water column may be moving at the rate of, say, 6 feet per second. The motion of this column of water cannot be suddenly arrested, consequently the pressure in the combustion chamber falls below that of the atmosphere, the exhaust valve opens under its own weight, and the forward movement of the water continuing, the level of the water in the combustion chamber finally falls below that of the water in the supply tank, and water rushes in through the valves in the valve box. When the kinetic energy of the moving water column becomes exhausted by forcing water into the elevated tank, the water column commences to flow back along the discharge pipe and gains velocity until, rising in the combustion chamber and driving the .spent gases out through the exhaust

valve, it reaches the exhaust valve, which it shuts by impact. The closing of the exhaust valve automatically locks itself and unlocks the inlet valve. Above this level a cushion of spent gas (highly diluted by air where a scavenging valve is used) is trapped, and is further compressed by the moving water column to a higher pressure than that due to the static head of water in the elevated tank. The column finally comes to rest. The pressure in the combustion chamber head is now sufficient to cause the water column to surge back again. The water column attains considerable momentum, and the pressure in the combustion chamber head falls below atmospheric pressure. As the inlet valve is now unlocked and the exhaust locked, a charge of explosive mixture is drawn in through the inlet valve until the column comes to rest again. The water column commences to return. The pressure in the combustion chamber rises, allowing the inlet valve to close, automatically lock itself, and unlock the exhaust valve. All valves are now closed, and the water column expends its energy in compressing the new charge, which it fires automatically, thus starting a fresh cycle of operations. The ignition is timed by a small piece of apparatus which closes the electric circuit at the point of maximum compression, a small battery, coil, and sparking plug similar to those used in motor car work being employed. The pump has the advantage over the ordinary gas engine of expanding its exploded gases to atmospheric pressure in its combustion chamber. .Briefly the working cycle is : A long out stroke: Exploded charge expands to pressure below atmosphere; supply of water taken in (where used, scavenger valve admits air). A return stroke: Spent gases (highly diluted by air when scavenger valve in use) driven out through exhaust valve; exhaust valve shuts and unlocks inlet valve; further compression of balance of spent gas in combustion head. A short outstroke: Expansion of compressed spent gas; fresh explosive charge enters through inlet valve, lieturn stroke Inlet valve closed and locked; exhaust valve unlocked; compression of explosive charge; ignition of same follows. REFERRING TO THE DIAGRAM A to B.Explosive charge being compressed. B. —Charge fired. B to C. —llise of pressure due to explosion of charge. C to D.—Gases expanding and doing work upon water column. D.—Exhaust valve opens. D to F.—Pressure in pump chamber remains atmospheric; water supply taken through water valves; water column surging back drives spent gases through exhaust valve; closes water valves. F.-Exhaust valve closed and locked; inlet valve unlocked. F. to G.—Compression of cushion of spent gases in combustion chamber head. G to H.Cushion expanding causing outstroke of water column; pressure in combustion chamber falling slightly below atmosphere, the inlet valve opens and admits fresh charge. J.—lnlet valve closes and locks; unlocks exhaust valve water column returning compress explosive charge, which it fires at K, commencing fresh cycle of operations.