James Watt’s Steam Engine:

James Watt’s Steam Engine:

In 1763, James Watt was working as instrument maker at the University of Glasgow when he was assigned the job of repairing a model Newcomen engine and noted how inefficient it was.

Out walking one Sunday afternoon in 1765, Watt sees the solution. He envisions a separate chamber in which the steam can condense. This means no more need for cooling and reheating, making the engine faster and more fuel efficient. His insights will convert a machine of limited use into one that will power the industrial revolution.

In 1765, Watt conceived the idea of equipping the engine with a separate condensation chamber, which he called a "condenser". Because the condenser and the working cylinder were separate, condensation occurred without significant loss of heat from the cylinder. The condenser remained cold and below atmospheric pressure at all times, while the cylinder remained hot at all times.

Steam was drawn from the boiler to the cylinder under the piston. When the piston reached the top of the cylinder, the steam inlet valve closed and the valve controlling the passage to the condenser opened. The condenser being at a lower pressure, drew the steam from the cylinder into the condenser where it cooled and condensed from water vapor to liquid water, maintaining a partial vacuum in the condenser that was communicated to the space of the cylinder by the connecting passage. External atmospheric pressure then pushed the piston down the cylinder.

The separation of the cylinder and condenser eliminated the loss of heat that occurred when steam was condensed in the working cylinder of a Newcomen engine. This gave the Watt engine greater efficiency than the Newcomen engine, reducing the amount of coal consumed while doing the same amount of work as a Newcomen engine.

Watt's next improvement to the Newcomen design was to seal the top of the cylinder and surround the cylinder with a jacket. Steam was passed through the jacket before being admitted below the piston, keeping the piston and cylinder warm to prevent condensation within it. The second improvement was the utilisation of steam expansion against the vacuum on the other side of the piston. The steam supply was cut during the stroke, and the steam expanded against the vacuum on the other side. This increased the efficiency of the engine, but also created a variable torque on the shaft which was undesirable for many applications, in particular pumping. Watt therefore limited the expansion to a ratio of 1:2 (i.e. the steam supply was cut at half stroke). This increased the theoretical efficiency from 6.4% to 10.6%, with only a small variation in piston pressure. Watt did not use high pressure steam because of safety concerns.

These improvements led to the fully developed version of 1776 that actually went into production.

As fully developed, it used about 75% less fuel than a similar Newcomen one.

The Watt steam engine, alternatively known as the Boulton and Watt steam engine, was the first practical steam engine and was one of the driving forces of the industrial revolution. James Watt developed the design sporadically from 1763 to 1775 with support from Matthew Boulton. Watt's design saved significantly more fuel compared to earlier designs that they were licensed based on the amount of fuel they would save. Watt never ceased developing the steam engine, introducing double-acting design.

James Watt's improvements to the steam engine "converted it from a prime mover of marginal efficiency into the mechanical workhorse of the Industrial Revolution". The availability of efficient, reliable motive power made whole new classes of industry economically viable, and altered the economies of continents. In doing so it brought about immense social change, attracting millions of rural families to the towns and cities.

In 1785 he and Boulton were elected fellows of the Royal Society of London.Watt established in 1794 the new firm of Boulton & Watt, which built the Soho Foundry to manufacture steam engines more competitively. In 1784 Watt makes further improvements to the steam engine and patents a steam locomotive. By 1790, both Boulton & Watt are wealthy men.