The phrase "a sort of shell" is correct and usable in written English.
It can be used to describe something that resembles or functions like a shell, often in a metaphorical sense.
Example: "The building had a sort of shell that protected it from the harsh weather outside."
Alternatives: "a kind of shell" or "a type of shell".
"At Machine we use the gallery as a sort of shell," Mr. Allen said.
It's a sort of shell which fits over the phone, and then you position your hands on the back, and you effectively have a Qwerty keyboard.
The larger, cooler stream is then fed into the chamber through holes along a "combustion liner" (a sort of shell) to reduce the overall temperature to a level suitable for the turbine inlet.
Interestingly, the Google tools the system uses make it far more interesting – making it a sort of shell for Google that is very unique.
For example, in a sort of shell game, they challenged chimps to remember which of three containers hid a tasty morsel of food.
According to a detailed investigation that the Times released on Monday, Seabrook has used his position as the head of the Corrections Department Benevolent Association to construct a sort of shell around Rikers, defending it from external pressures or prosecutors like Bharara via Frank Underwood style politicking.
It's powerful stuff, and very good at invoking a sense of listlessness and a sort of shell-shock at the horrors of life.
There's an immense meteoric sculpture, a sort of crashed shell which enshrouds the Kubrick room, and it is built of shapes culled from his paintings; laser-cut shards that migrated from paint to digital to tangible, piece by piece.
"I think we were all sort of shell-shocked," Rebecca Saeger, executive vice president and chief marketing officer of the Charles Schwab Corporation, said in recalling last year.
In the ashtray she sees a sort of dugout, possibly a shell crater with soldiers lying heaped together in hideously contorted positions, all dead.
